CUET-UG 2022: How NTA will ensure equity in evaluation of candidates appearing for the same paper on different days

The Indian Express explains this process, which is used even in the case of JEE (Main) held by the NTA, which is an autonomous body under the Ministry of Education:

Q. What is the normalisation?
The CUET-UG is a computer-based test and will be held on multiple dates between July 15 and August 20. As a result, there will be different sets of question papers on different days for every subject. Naturally, there may be variations in the difficulty level of question papers on the same subject. Moreover, in the case of CUET-UG, there are apprehensions that candidates taking the test in the initial set of dates may not perform as well as those who will appear for the test in August (and hence will have more time to prepare). The normalisation formula will address these concerns by ensuring that candidates are neither benefitted nor disadvantaged due to such factors.

Q. How is normalisation applied?
To ensure equity, the NTA will assess the candidates using percentile scores instead of their raw marks. Percentile scores are scores based on the relative performance of all those who appear for a paper in a particular session. The raw marks obtained by an examinee in a paper are converted into a scale ranging from 100 to 0 to show where she stands with reference to other candidates who appeared for the same paper in the same session. As a result, the toppers of two different sessions may have scored different marks, but both their percentile scores will be 100. This is because a 100 percentile score indicates that a candidate has performed better than everyone else in her cohort in the same session. Hence, all the highest raw marks in each session of a paper would be normalized to 100 percentile score. The scores of the remaining candidates will be relative to that of the topper of a particular session only.

Q. What is the mathematical formula used for arriving at a normalised percentile score
To calculate the normalised percentile score of a candidate, three variables are required: the raw marks of the candidate (A), the total number of candidates with a score equal to or less than her raw score (B), and the total number of candidates in that particular session (C). The mathematical formula applied is B divided by C multiplied by 100 (B/C*100). For example, take the hypothetical case of a student who appears in a session with 41,326 other candidates. Say, she obtains 121 marks, scoring more than 37,244 other candidates of her session. Her normalised percentile score will be 37244/41326*100 or 90.1224411 (percentile scores will be calculated up to 7 decimal places).

Q. What do the percentile scores indicate?
A candidate’s percentile score indicates the proportion of examinees who have scored equal to or less than the candidate in that particular session. Simply put, 100 percentile indicates that 100 per cent candidates of a particular session have scored equal to or less than the topper. A student with a percentile score of 70 would indicate that she has scored more than 70 per cent of the candidates of her session.